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FreeBSD-SA-16:22.libarchive                                 Security Advisory
                                                          The FreeBSD Project

Topic:          Directory traversal in cpio(1)

Category:       contrib
Module:         libarchive
Announced:      2016-05-31
Credits:        Alexander Cherepanov
Affects:        All supported versions of FreeBSD
Corrected:      2016-05-21 09:03:45 UTC (stable/10, 10.3-STABLE)
                2016-05-31 16:35:03 UTC (releng/10.3, 10.3-RELEASE-p4)
                2016-05-31 16:33:56 UTC (releng/10.2, 10.2-RELEASE-p18)
                2016-05-31 16:32:42 UTC (releng/10.1, 10.1-RELEASE-p35)
                2016-05-21 09:27:30 UTC (stable/9, 9.3-STABLE)
                2016-05-31 16:23:56 UTC (releng/9.3, 9.3-RELEASE-p43)
CVE Name:       CVE-2015-2304

For general information regarding FreeBSD Security Advisories,
including descriptions of the fields above, security branches, and the
following sections, please visit <URL:https://security.FreeBSD.org/>.

I.   Background

The libarchive(3) library provides a flexible interface for reading and
writing streaming archive files such as tar(1) and cpio(1), and has been the
basis for the FreeBSD implementation of the tar(1) and cpio(1) utilities
since FreeBSD 5.3.

II.  Problem Description

The cpio(1) tool from the libarchive(3) bundle is vulnerable to a directory 
traversal problem via absolute paths in an archive file.

III. Impact

A malicious archive file being unpacked can overwrite an arbitrary file on
a filesystem, if the owner of the cpio process has write access to it.

IV.  Workaround

No workaround is available.

V.   Solution

Perform one of the following:

1) Upgrade your vulnerable system to a supported FreeBSD stable or
release / security branch (releng) dated after the correction date.

Reboot is not required.

2) To update your vulnerable system via a binary patch:

Systems running a RELEASE version of FreeBSD on the i386 or amd64
platforms can be updated via the freebsd-update(8) utility:

# freebsd-update fetch
# freebsd-update install

Reboot is not required.

3) To update your vulnerable system via a source code patch:

The following patches have been verified to apply to the applicable
FreeBSD release branches.

a) Download the relevant patch from the location below, and verify the
detached PGP signature using your PGP utility.

[FreeBSD 10.x]
# fetch https://security.FreeBSD.org/patches/SA-16:22/libarchive-10.patch
# fetch https://security.FreeBSD.org/patches/SA-16:22/libarchive-10.patch.asc
# gpg --verify libarchive-10.patch.asc

[FreeBSD 9.3]
# fetch https://security.FreeBSD.org/patches/SA-16:22/libarchive-9.patch
# fetch https://security.FreeBSD.org/patches/SA-16:22/libarchive-9.patch.asc
# gpg --verify libarchive-9.patch.asc

b) Apply the patch.  Execute the following commands as root:

# cd /usr/src
# patch < /path/to/patch

c) Recompile the operating system using buildworld and installworld as
described in <URL:https://www.FreeBSD.org/handbook/makeworld.html>.

VI.  Correction details

The following list contains the correction revision numbers for each
affected branch.

Branch/path                                                      Revision
- -------------------------------------------------------------------------
stable/9/                                                         r300363
releng/9.3/                                                       r301044
stable/10/                                                        r300361
releng/10.1/                                                      r301046
releng/10.2/                                                      r301047
releng/10.3/                                                      r301048
- -------------------------------------------------------------------------

To see which files were modified by a particular revision, run the
following command, replacing NNNNNN with the revision number, on a
machine with Subversion installed:

# svn diff -cNNNNNN --summarize svn://svn.freebsd.org/base

Or visit the following URL, replacing NNNNNN with the revision number:

<URL:https://svnweb.freebsd.org/base?view=revision&revision=NNNNNN>

VII. References

<URL:https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2015-2304>

The latest revision of this advisory is available at
<URL:https://security.FreeBSD.org/advisories/FreeBSD-SA-16:22.libarchive.asc>
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